something faulty. But what?

Good Day. Please can you help me. I am using a
Intel p3 with 733m cpu and 384m ram
I have audio, graphics and sound cards plugged in as there are no
connections for these on the motherboard.
When trying to install their drivers it brings up error in ipppd and
isdn and it cant find makedev.
Even when installing down loaded updates it brings up these errors.
I am very new to ubuntu 9.04 as I have only used windows till now and
don't want to go back there. Is there a way I can uninstall these
packages and reinstall them. And is it possible to reinstall 9.04 over
the existing one without losing all downloaded updates and upgrades that
worked? If so, please can you tell me how.
I am using a cellphone as a modem through a data cable.
Looking forward to some enlightenment.
Thank you.
Miles Sharpe
Pretoria
South Africa